Aspirating nozzle



A ril 19, 1966 A. BIBER ETAL. 3,246,353

ASPIRA'IING NOZZLE Original Filed April 29, 1960 9 Sheets-Sheet 1INVENTORS. ALBERT BIB'ER ORVIS A. DAVIS, SR. BRUCE R. WALSH 9Sheets-Sheet 2 A. BIBER ETAL ASPIRA'IING NOZZLE INVENTORS. ALBERT BIBERORVIS A. DAVIS, SR. BRUCE R. WALSH 9 Sheets-Sheet 3 Original Filed April29, 1960 CURVE B CURVE A O.l|O O.|2O

DIAMETER OF SECOND ORIFICE, INCHES b r 2 ll INVENTORS. ALBERT BIBERORVIS A. DAVIS, SR. BRUCE R. WALSH April 1956 A. BIBER ETAL 3,246,853

ASPIRATING NOZZLE Original Filed April 29, 1960 9 Sheets-Sheet 4 [I56I58 '54 mm hid]:

INVENTORS. ALBERT BIBER 5 ORVIS A. DAVIS, SR. 16

%, BRUCE R. WALSH April 19, 1966 BlBER T L, 3,246,853

ASPIRATING NOZZLE Original Filed April 29, 1960 9 Sheets-Sheet 5INVENTORS ALBERT BIBER ORVIS A. DA SR. BRUCE R. W H

April 19, 1966 I A. BIBER ETAL ASPIRATING NOZZLE Original Filed April29. 1960 9 Sheets-Sheet 6 j IN VE N TORS.

ALBERT BIBER O S A. DAVIS, SR. BR E R. WALSH April 9, 1966 A. BIBER ETAL3,246,853

ASPIRATING NOZZLE Original Filed April 29, 1960 9 Sheets-Sheet 7INVENTORS ALBERT BIBER OR A. DAVIS, SR. 8: BR R. WALSH April 19, 1966 A.BIBER ETAL 3,246,853

IASPIIRA'IING NOZZLE Original Filed April 29. 1960 9 Sheets-Sheet 8 LALB INVENTORS ERT ER, ORVIS A.D 3 SR. 6. BRUCE R. wALH APril 9, 1966 A.BIBER ETAL 3,246,853

SPIRA'IING NOZZLE Original Filed April 29, 1960 9 Sheets-Sheet 9INVENTORS. ALBERT BIBER,

IS A. DAVIS, SR. 8 CE R. WALSH United States Patent 3,246,853 ASPIRATINGNQZZLE Albert Biber, Verona, Orvis A. Davis, Sn, Gibsonia, and

Bruce R. Walsh, Pittsburgh, Pa, assignors to Gulf Research & DevelopmentCompany, Pittsburgh, Pa., a corporation of Delaware Application Dec. 11,1963, Ser. No. 32?,808, which is a continuation of application Ser. No.111,821, May 22, 1961, which is in turn a continuation of applicationSer. No. 25,732, Apr. 29, 196i). Divided and this application dune 1,1965, Ser. No. 460,454

2 Claims. (Cl. 239403) This application is a division of copendingapplication Serial Number 329,808, filed December 11, 1963. The parentapplication was a continuation of Serial Number 111,821, filed May 22,1961, now abandoned, which in turn was a continuation of Serial Number25,732, filed April 29, 1960, now abandoned.

This invention relates to aspirating nozzles wherein an aspi-ratingfluid is employed to aspirate into a nozzle either a single or aplurality of other fluids. The aspirating fluid employed is generally asingle gas such as air. The air or other aspirating gas is generallyemployed at a pressure only slightly superatmospheric, for example, at apressure of about 2 to pounds per square inch gauge. The 2 pound persquare inch gauge pressure is employed when it is desired to aspirate arelatively small amount of fluid and the 10 pound per square inch gaugepressure is employed when it is desired to aspirate a relatively largeamount of fluid into the nozzle.

It has been found that by employing air as an aspirating gas at apressure of only 3 pounds per square inch gauge to aspirate into thenozzle liquid fuel oil which is at atmospheric pressure, an atomizedfuel in air spray admixture is produced which when burned produces aflame which is much more compact and much less smoky as compared to theflame which is achieved when the oil is the substance that is umped,even at pressures of 80 to 100 pounds per square inch gauge and even ifatmospheric air is aspirated. Furthermore, the use of an aspirating gasto draw fuel oil into the nozzle solves serious nozzle operationalproblems since it permits the oil ducts in the nozzle to be ofrelatively large transverse cross section thereby permittingunobstructed oil passage. On the other hand, when the oil is chargedunder pressure, in order to achieve an equivalent oil flow rate it isnecessary to employ oil ducts of such restricted transverse crosssectional area that frequent plugging occurs due either to diflicultlyremovable solid impurities in the oil or to fuel carbonization caused byhigh nozzle temperatures.

In accordance with this invention a single aspirating fluid can producea wide variety of advantageous mixtures. For example, aspirating air candraw into a nozzle a single liquid fuel oil to produce a spraycomprising an admixture of the air and oil. Also, aspirat-ing air candraw into a nozzle a first liquid fuel of one grade and a second liquidfuel of another grade to produce a spray comprising a fuel oil blend inadmixture with air. Again, aspirating air can draw into a nozzle both aliquid fuel oil and an additive for the oil, such as a corrosioninhibitor, to produce a spray comprising air, fuel oil and additive.Additionally, a gaseous fuel at slightly superatmospheric pressure canbe employed as an aspirating medium to draw into the nozzle liquid fueloil and atmospheric air to produce a spray comprising gaseous fuel,liquid fuel andair. Nozzles of this invention can be constructed wherebythree or more different components are drawn into the nozzle by means ofthe aspirating fluid to produce a corresponding spray comprisingfour-ormo-re components. Also, instead of aspirating a plurality of Icefluids the nozzles of this invention can be employed to aspiratemultiple portions of a single fluid, such as a fuel E11, dto increasethe capacity of the nozzle in regard to that The aspirating nozzles ofthis invention comprise a plurality of enclosed swirl chambers eachhaving a substantially circular cross section, an axial dischargepassage is disposed at the forward end of said swirlchamber thenarrowest portion of which constitutes a discharge orifice, swirlingmeans is disposed at the rear of said swirl chamber, a tubular ductextends axially from the rear of said swirl chamber and terminates withan axial opening at an intermediate axial position in said swirl chamberbetween said swirling means and said discharge orifice,- the diameter ofsaid discharge orifice is larger than the internal diameter of saidtubular duct, the outer surface of said tubular duct has a cylindricalconfiguration over substantially its entire length, said nozzle is'freeof means for imparting swirling to a fluid flowing within and from saidtubular duct, said swirl chamber wall surface either converges uniformlyconically from said swirling means disposed to the rear of the axialterminus of said tubular duct to said discharge orifice or extends as auniform cylinder from said swirling means disposed to the rear of theaxial terminus of said tubular duct to said discharge orifice, saidswirling means at the rear of said swirl chamber comprises swirlingpassageway means having swirling opening means which approach and .entersaid swirl chamber in both a forwardly and substantially tangentialdirection with respect to said conical or cylindrical swirl chainberwall surface adapted for the admission of a swirling pressurized gas inboth a forwardly and substantially tangential direction with respect tosaid conical or cylindrical wall surface, said swirl chamber having rearenclosure means extending from the exterior of said tubular duct so thatsaid swirl chamber is substantially completely enclosed at the rearthereof, and said opening means extends through not more than a minorproportion of the surface of the rear wall of said swirl chamber.

This invention will be more completely understood by reference to theattacheddrawings in which FIGURES l, 2, 3, 5, 6, l2, 13, 14, 16, 17 and18 are views of multiple chamber nozzles, FIGURE 4 presents data curvesrelating to multiple chamber nozzles, and FIGURES 7, 8, 9, 10. 11 and 15are views of single chamber nozzles.

FIGURE 1 shows an elevational view of a longitudinal section through theaxis of a nozzle designated generally as 70 and having a tubular bodyportion 72 which is internally and externally threaded as shown. Theforward end of body portion 72 terminates with a substantially flatintegral enclosure 74 which is .on a plane transverse to the axis oftubular body 72. Enclosure 74 has an orifice opening 76 which is theapex of an axial conical bore 78.

A plug 80 having external threads and an axial bore 82 is equipped withtwo or more prongs 84 on its rear face so that it can be screwed intothe interior of tubular body 72 as shown. Plug 80 has a centralforwardly projecting stud 86 terminating with a frustoconical swirl stem88 which abuts firmly against the complementary interior surface of thebase portion of conical bore 78 leaving unoccupied the apex of conicalbore 78, said unoccupied apex constituting a swirl chamber 90. Swirlstem 88 has one or more peripheral slots 92 extending the length of thestem and providing passage between air chamber 94 and swirl chamber 90.Axial bore 82 constitutes a connecting passageway into swirl chamber forthe suction of a fluid which can be a gas but is advantageously a liquidsuch as, in this example, oil from an oil reservoir 83 disposed on alower level. Axial bore 82 protrudes a portion of the 3 distance intoswirl chamber by means of cylindrical tube 79.

A cap designated generally as encloses the forward outer portion oftubular body 72 and the end enclosure 74 of tubular body 72. FIGURE 2 isa view of the cross section taken on plane 2-2 of FIGURE 1. Cap 95 has aside portion 96, a top portion 9 8 and an orifice opening in the centerof the top portion which opening is larger than orifice opening 76. Cap95 is screwed in sealing engagement with tubular body 72 and the topportion 98 is spaced apart from enclosure 74 to form a chamber 102. Ahollow rib 104 which is integral with side 96 of cap 95 has an interiorchamber 106 from which one or more passageways 108 approach chamber 102.Passageways 108 can approach chamber 102 radially but preferablyapproach chamber 102 tangentially as shown in FIGURE 2. An inlet passage110 to space 106 is provided through the interior of boss 130.

A cylindrical duct 134 extends from orifice 76 axially into cylindricalorifice 100. Duct 134 can extend a portion of the distance to orifice100 but if such a duct is employed it preferably extends into orifice100, as shown. The outer diameter of duct 134 is less than the diameterof orifice 100, providing a diameter differential therebetween. Byextending the duct into orifice 100, the aspirational effect is exertedupon chamber 102 with :a diminished divergence of spray from swirlchamber 90 during transit through orifice 100, thereby permitting thediameter of orifice 100 to be smaller than that which would be requiredin the absence of duct 134. Where a multiplicity of nozzle caps areemployed, as illustrated in FIGURE 6, this consideration becomesincreasingly important.

After the plug 80 is screwed tightly in the interior of tubular body 72and the cap 95 is screwed onto the exterior of tubular body 72 as shownthe resulting nozzle assembly is secured into position for use, forexample, by screwing tubular body 72 into a furnace wall 112. After thenozzle is assembled and secured into place, oil reservoir 83 which isopen to the atmosphere is connected to the nozzle at externally threadedboss 114 extending rearwardly from the center of plug 80 and coaxialwith oil passageway 82. Suitable flared tubing 116 is attached insealing connection to boss 114 by means of nut 118. Aspirating fluidflows to chamber 94 from pressurized chamber 127 through valve andpassageway 120 in plug 80 terminating with rearwardly extendingexternally threaded boss 122 to which flared tubing 124 is attached insealing connection by means of internally threaded nut 126. Theaspirating fluid can be a liquid but is preferably a gas at a slightlysuperatmospheric pressure such as, in this example, air at 3 pounds persquare inch gauge. Whatever the pressure of the air it must be at apressure higher than the fluids under aspiration. A second body of fluidunder aspiration such as liquid fuel oil of the same or, as in thisexample, a different grade than that contained in reservoir 83 issupplied to chamber 106 through passageway 110 from reservoir 111,vented to atmosphere, by attaching flared tubing 128 equipped with valve113 in sealing connection with boss 130 by means of nut 132. Tubes 128and 124 are tied into each other by means of connecting tube 136 havinga valve 138.

In operating the nozzle shown in FIGURES 1 and 2 to aspirate the fluidsin both reservoir 83 and reservoir 111, slightly superatmospheric air ischarged through air passageway 120 to air chamber 94 from which it ispassed through slots 92 and approaches swirl chamber 90 in asubstantially tangential manner. The air swirls in swirl chamber 90creating an evacuated axial vortex which draws a first grade of fuel oilfrom reservoir 83 through tube 116, axial passageway 82 and duct 79 intoswirl chamber 90 to form a first mixture of air and oil. Duct 79 allowsthe air to assume an adequate swirling and axial pattern of movementprior to exposure of oil to it. The cylindrical configuration of theouter surface of duct 79 prevents transverse motion of air across itsopen end, thereby preventing air back pressure against oil from thereservoir. In the absence of duct 79 no aspiration of oil from thereservoir would occur. The mixture passes through orifice opening 76 andduct 134 into second orifice 100 where, with valve 138 being closed, itaspirates into itself a second grade of oil from reservoir 111 whichenters chamber 102 through tube 128, having open valve 113, bore 110,annulus 106 and tangential slots 108 to form a second mixture of air anda blend of two oils of different grades which mixture is then emittedthrough orifice 100. The quantity of oil aspirated from reservoir 111depends upon the diiferential diameter between duct 134 and orifice 100.Also, the quantities and proportions of oil from reservoirs 111 and 83being blended by the nozzle can be adjusted externally by regulation ofvalves 1 13 and 85, respectively. Operation of the nozzle can beterminated merely by closure of air valve 125 without ensuing drippageof oil from the nozzle by virtue of oil reservoirs 111 and 83 beingdisposed below nozzle level.

FIGURE 3 shows a plan View of a longitudinal section through the axis ofa nozzle designated generally as 140 which is similar to the nozzleillustrated in FIGURES l and 2 except in two respects. The firstdifference is that duct 134 shown in FIGURE 1 is omitted so that orifice76 discharges directly into the rear of chamber 102. The second is thatthe diameter of orifice 142 is larger than the corresponding dimensionsof orifice 100 shown in FIGURE 1. Since the spray from swirl chamber 90has the general configuration of a cone whose apex is at the point ofemission from the chamber, the absence of duct 134 results ineffectively transposing the spray rearwardly so that its transversediameter at the orifice 142 is greater by an amount dependent upon thelength of duct 134, as compared with the spray produced with the use ofa duct 134. Accordingly, orifice 142 is larger than orifice 100.

In a highly important aspect the nozzle of FIGURE 3 is preferred overthe nozzle of FIGURE 1. It was found in testing two substantiallyidentical nozzles differing from each other only in that the firstpossessed a duct similar to the duct 134 of FIGURE 1 and the second wasdevoid of such a duct, as shown in FIGURE 3, that a greater fuel oilaspiration rate was possible with the second nozzle. Each nozzleaspirated ASTM Number 2 fuel oil under atmospheric pressure in both thefirst and second chambers in the manner outlined in the abovedescription of operation of the nozzle of FIGURE 1. All tests were madewith aspirating air at a pressure of 3 pounds per square inch gauge, anair fiow rate of approximately 42 cubic feet per hour and a fuel oillift of one inch. Data were taken by testing each nozzle followingstepwise increases of the second chamber orifice diameter accomplishedby machining progressively larger cylindrical second orifice bores. Theresults are shown in FIGURE 4 wherein curve A represents the data takenwith a nozzle possessing a duct 134 as shown in FIGURE 1 and whereincurve B represents the data taken with a nozzle devoid of such a duct asshown in FIGURE 3. The only variable adjusted for each nozzle was the;diameter of the second orifice. As shown in FIGURE 4,.

under similar conditions the nozzle of FIGURE 3 is: capable of a greateraspiration rate of fuel oil than is;

the nozzle of FIGURE 1.

It is noted that a nozzle similar to that employed inobtaining the datashown in curves A and B of FIGURE. 3 except that the second chamber capwas removed, thereby converting it into a single chamber nozzle, wascapable of aspirating only 0.54 gallon per hour of ASTM Number 2 fueloil with 3 pounds per square inch gauge air and a one-inch oil life. Inall tests made the orifice diameter of the first chamber was 0.087inches... FIG- URE 4 shows that in the case of curve A, the optimum flowoccurs at an orifice diameter ratio of 1.38, while ratios between 1.2and 1.5 generally and between 1.3 and 1.5 preferably are desirable. Theoptimum ratio for curve B is 1.56 while ratios between 1.2 and 2.0generally and between 1.3 and 1.8 preferably give good results. There isless criticality in diameter ratios and better aspiration rates inrespect to curve B as compared to curve A.

FIGURE 5 shows still another multiple fluid aspirating nozzle of thisinvention. It is seen that the nozzle of FIGURE 5 is generally similarto that of FIGURE 3 but that a forward chamber has been added. As shownabove, the nozzle of FIGURE 3 is a highly effective aspirating'device.However, it has been found that upon combustion of a fuel-air spray fromthe nozzle of FIG- URE 3, the flame can be improved in two importantrespects by the modification of the nozzle as shown in FIGURE 5.

The nozzle of FIGURE 5 incorporates a forward swirl chamber onto thenozzle of FIGURE 3 by screwing onto cap '95 a similar but larger cap150, as shown, to form swirl chamber 152 therebetween. Swirl chamber 152is connected to a source of pressurized fluid 154, preferably a gassource such as air at 3 pounds per square inch gauge, which is suppliedthrough tubing 156, regulated by valve 158. The pressurized air passesinto annulus 160 and thence tangentially into swirl chamber 152 throughtangential inlet port 162. In order to prevent back pressure againstorifice 142 .a cylindrical duct 164 extends outwardly from orifice 142at least a portion of the distancealong the length of cylindricalchamber 166. The cylindrical configuration of the outer surface of duct164 prevents transverse movement of pressurized air across the openingof the duct. Any transverse movement of pressurized air across the ductopeningwould create a back pressure in the nozzle and render the nozzleinoperative. Superatmospheric air entering'through tangential inlet'port162swirls in swirl chamber 152 and outwardly through chamber 166 whereit draws into itself the mixture passing through duct 164.

The respects in which incorporation of the forward swirl chamberillustrated in FIGURE 5 improves the nozzle of FIGURE 3 are: first,combustion of the spray is rendered more complete by virtue of ahighair-fuel ratio as evidenced by both dimution of yellowish flamecoloration and elimination of slight traces of visible smoke and theflame is rendered more highly compact. Improvement of both thecombustion and physical characteristics of the flame in this manner,coupled with the demonstrated high aspirational efliciency of the basicnozzle of FIG- URE 3, renders the nozzle" of FIGURE 5 a highlyadvantageous nozzle.

A single tluid aspirating nozzle is similarly improved by provision of aforward swirl chamber of the type illustrated in FIGURE 5. In thisregard, referring to FIGURE 1, closureof valve 113 and opening of valveURE 3, renders the nozzle of FIGURE 5 a highly advantageous single fluidaspirating nozzle improved with a forward swirl chamber.

The nozzle shown in FIGURE 6 illustrates the use of an intermediateseries of chambers, rather than only a single intermediate chamber asshown in FIGURE 5, for the purposeof increasing the number of fluidsbeing aspirated into the nozzle. Whereas the nozzle of FIG- URE l iscapable of aspirating inwardly two fluids, one from reservoir 83' andanother from reservoir 111, the nozzle of FIGURE 6by the addition ofintermediate cap 170 is capable of inward aspiration of a third fluidfrom reservoir 172, through tube 173 and valve 174, annulus 176,tangential opening 178 and chamber 130. The diameter of orifice 181 islarger than the diameter of generally cylindrical duct 133 and thediameter of orifice 185 is larger than the diameter of generallycylindrical duct 187 by an amount sufiicient to accomplish substantialaspiration of nonpressurized fluid into chambers and 188, respectively.More than one fluid could be aspirated into a single chamber to avoidutilization of a series of chambers but such would entail extremedifiiculties in construction. Cap 182 forms a swirl chamber 184 to whichair is supplied from pressurized air reservoir 154 in accordance withthe description of the nozzle of FIG- URE 5.

FIGURE 7 illustrates a single chamber nozzle designated generally asnozzle 120. FIGURE 8 is a view taken through the section 88 in FIGURE 7.FIGURE 7 shows a plan view of a longitudinal axial section of nozzlemaintained in position by a suitable support 192. Nozzle body 194 has aforward orifice 196 and is externally and internally threaded as shown.Frustoconical swirl stem 198 abuts in sealing engagement against acomplementary internal surface in the forward portion of nozzle body 194to form a conical swirl chamber 200 between it and orifice 196.Alternately, swirl chamber 200 could be cylindrical rather than conicalby appropriate modification of nozzle body 194. A plug 202 is screwed insealing engagement with the internal surface of the rearward portion ofnozzle body 194 to define an aspirating air chamber 204 between it andswirl stem 198. Plug 202 has a longitudinal bore 206 through whichaspirating air is supplied through tube 210 from a pressurized airsource 208. Air entering chamber 204 passes through one or moreperipheral slots 212 on swirl stem 198 which enter swirl chamber 200both in a forward direction with respect to the conical wall surface ofswirl chamber 200, as is shown in FIGURE 7, and substantiallytangentially with respect to the conical wall surface of swirl chamber200, as is shown in FIGURE 8. Since slots 212 enter swirl chamber 200both in a forwardly direction with respect to the conical wall surfaceof swirl chamber 200, as is shown in FIGURE 7, and substantiallytangentially with respect to the conical wall surface of swirl chamber200, as is shown inFIGURE 8, the air passing through slots 212 entersswirl chamber 200 in both a forwardly and a substantially tangentialdirection with respect to the conical wall surface of swirl chamber 200.Swirl stem 198 and plug 202 are each equipped with an axial longitudinalbore. Axial tube 216 extends through the axial bores in swirl stem 108and plug 202 in sealing engagement therewith from the rear of the nozzleinto swirl chamber 200 for a portion of the length thereof. Swirl stem198 constitutes means for enclosing the rear of swirl chamber 200 andthe forward face of swirl stern 198 extends between the exterior oftubular duct 216 and the conical swirl chamber wall surface tosubstantially completely enclose the rear of the swirl chamber.Aspirating gas inlet groove 212 extends through not more than a minorproportion of the rear wall surface of swirl chamber 200. Groove 212 isconfined only to a region laterally remote from tubular duct 216 andclose to the swirl chamber wall surface. The rear of tube 216 extendsdownward intothe fluid contained in reservoir 224. Tube 216 extends agreater distance into swirl chamber 200 from the rear thereof than thedistance of the opening of the aspirating gas inlet groove 212 from therear of the swirl chamber. In this manner air entering throughtangential slot 212 has an opportunity to assume both a swirling andaxial pattern of movement and travel past the opening of tube 216 in adirection which is parallel to the nozzle axis, thereby permitting asuction to be exerted at this opening to which is exposed the fluid influid storage reservoir 224. While swirl chamber 200 is equipped withmeans for inducing swirling therein, the nozzle is free of means forimparting swirling to fluid flowing from axial duct 216-. The narrowestportion of discharge orifice 1% is larger than the internal diameter ofaxial duct 216 and the wall surface of swirl chamber 200 convergessubstantially conically from aspirating gas inlet groove 212 at aposition to the rear of the axial terminus of axial duct 216 to thenarrowest portion of the discharge orifice.

FIGURE 9 shows a single chamber aspirating nozzle which is adapted forthe aspiration of a plurality of fluids and which is designatedgenerally as nozzle 234). FIG- URE 9 shows a longitudinal axialsectional plan view of nozzle 230 secured fixedly in place by a support232 and FIGURE 10 is a view facing the section Iil10 of FIG- URE 9.Nozzle 230 has a plurality of coaxial and concentric ducts formingannular spaces therebetween. FIG- ure 9 shows outer, intermediate andinner concentric cylindrical ducts designated as ducts 236, 238 and 240,respectively. Ducts 236, 238 and 24% extend from fluid reservoirs 242,244 and 246, respectively. The fluids in reservoirs 2-42 and 244 areexposed to the swirling gas vortex in swirl chamber 234 through annularspaces 248 and 250, respectively, while the fluid in reservoir 246 isexposed to the swirling gas vortex in swirl chamber 234 through theinterior of tube 240. As shown, inner tube 240 extends the greatestaxial distance into swirl chamber 234, intermediate tube 238 extends anintermediate distance and outermost tube 236 extends the smallest axialdistance thereinto but this smallest distance is still a greaterdistance from the rear of swirl chamber 234 than is the distance of thetangential inlet ports of swirling gas slots 256 from the rear of theswirl chamber. In this manner the aspirating gas entering swirl chamber234 through tangential inlet slots 256 has an opportunity to form aswirling gas vortex prior to exposure of fluid in annular space 248thereto. The swirling gas in its axial movement through swirl chamber234 aspirates fluid first from annular space 248 to form a first mixturewhich mixture then has an opportunity to travel a further axial distancethrough the swirl chamber and assume an adequate swirl pattern prior toaspirating into itself fluid through annular space 256 to form a secondmixture. This second mixture then travels a further axial distancethrough swirl chamber 234 having an opportunity to itself assume anadequate swirl pattern prior to aspirating into itself the fluid frominnermost tube 240 to form a third mixture. This third mixture is thendischarged from the swirl chamber through orifice 258. The staggeredarrangement of concentric tubes 236, 238 and 240 in the swirl chamber234 is thereby seen to permit elficient inward aspiration of a pluralityof fluids into a single chamber.

FIGURE 11 shows a nozzle with a single swirl chamber 266 having auniform cylindrical configuration from the rearward end thereof todischarge opening 262 at its forward end. The rear wall of swirl chamber260 is defined by swirl stem 264 which is cylindrical in shape and whoseouter diameter is substantially equal to the diameter of swirl chamber265) in order to establish a fluid tight seal at the rear of the swirlchamber. One or more shallow slot means 266 extend the length of swirlstem 264 on the surface thereof and open into swirl chamber 260 in aforward and tangential direction with respect to the swirl chamber wallsurface. Slots 266 open into swirl chamber 260 only at a positionrelatively close to the wall surface thereof at a position which islaterally remote from axial duct 2'70 and to the rear of the openterminus of axial duct 270. Slot means 266 extend through not more thana minor proportion of the rear wall surface of the swirl chamber. Inoperation, pressurized air from chamber 268 passes through slot 266 andenters swirl chamber 260 in a forward and tangential direction withrespect to the swirl chamber wall surface. The air swirls within swirlchamber 260 and travels axially therethrough moving past the openterminus of axial duct 270 in a direction which is substantiallyentirely parallel with respect to the duct opening whereby fluid, suchas fuel oil, is freely aspirated through the open terminus of axial duct276). A mixture of air and oil is sprayed through nozzle dischargeopening 262.

FIGURE 12 shows the nozzle of FIGURE 11 modified by the addition of asecond swirl chamber. In FIG- URE 12, the mixture of fuel and air fromthe first swirl chamber is passed through a second cylindrical duct 272into a second swirl chamber 274. Second swirl chamber 274 is defined bya uniform axial cylindrical bore in threaded cap 276. The diameter ofswirl chamber 274 is greater than the diameter of second axial duct 272.Secondary pressurized air enters the second swirl chamber throughconduit 278, passageway 284), and clearance 282, and flows into one ormore slot means 284 on cylindrical swirl stem 286. Slot means 284 do notextend through more than a minor proportion of the rear wall surface ofsecond swirl chamber 274. Secondary air is directed into second swirlchamber 274 by slot means 284 in both a forward and tangential directionwith respect to the swirl chamber wall surface. The secondary air swirlswithin swirl chamber 274 and travels axially therethrough moving pastthe open terminus of duct 272 in a direction which is substantiallyentirely par allel with respect to the nozzle axis creating anaspirational effect upon the mixture of air and oil leaving first swirlchamber 266} and enriching the air content of said mixture.

FIGURE 13 shows the modification of the single conically shaped swirlchamber of FIGURE 7 by the addition of a second swirl chamber similar tothe second swirl chamber shown in FIGURE 12. Referring to FIG- URE 13,the mixture of air and a fluid, such as fuel oil, from the first swirlchamber travels through cylindrical duct 288 into a secondarycylindrical swirl chamber 290. Secondary air is admitted to swirlchamber 290 in a forwardly and tangential direction with respect to thewall surface thereof through tangential slot 292 on swirl stem 294.

In the nozzle of FIGURE 17 the first swirl chamber is cylindrical andthe second is conical. In the nozzle of FIGURE 18 the first and thesecond swirl chambers are both conical.

FIGURE 14 is a modification of the conically shaped single swirl chamberof FIGURE 9 which is adapted to aspirate a plurality of fluids through aplurality of staggered cylindrical ducts, designated as ducts 296, 298and 300. The nozzle of FIGURE 14 employs a secondary swirl chamberhaving a cylindrical configuration. A mixture of air and the fluidsdrawn through the staggered cylindrical ducts is passed throughcylindrical duct 302 into second swirl chamber 304. Secondary air isadmitted into second swirl chamber 304 through slot 306 on swirl stem308 and a swirling mixture enriched with secondary air is dischargedthrough second swirl chamber discharge opening 310.

FIGURE 15 shows a nozzle similar to the nozzle shown in FIGURE 11wherein the swirl chamber is cylindrically shaped, as shown at 312,except that a plurality of staggered axial tubes 314, 316 and 318 isutilized rather than a single axial tube as shown in FIGURE 11.Similarly, FIGURE 16 shows a nozzle which is similar to that shown inFIGURE 12 except that a plurality of staggered cylindrical axial tubes320, 322 and 324 extend into the first swirl chamber, rather than asingle axial tube as shown in FIGURE 12. The discharge orifice is largerthan the inside diameter of the largest tubular duct terminating infront thereof.

It is critical that the swirl chamber wall surface of the nozzle of thisinvention should be either the hollow inte rior surface of a uniformlyconverging cone having an open apex which defines a discharge orifice orthe hollow interior surface of a uniform cylinder. The conical orcylindrical swirl chamber surface extends from the rear of the openterminus of the axial cylindrical duct to the smallest axial opening infront of the open terminus of the axial cylindrical duct, which is thedischarge orifice. A uniform converging conical configuration or auniform cylindrical configuration permits the axial velocity of theswirling gas stream to remain relatively uniform during transit of theswirling gas stream along the length of the swirl chamber. A swirlchamber wall surface configuration which causesa substantial reductionin axial velocity of the swirling gas stream within the swirlchambershould be avoided. For example, a hemispherical swirl chamberwall surface configuration would cause the axial velocity of theswirling gas stream to diminish during transit of the swirling gasstream along the length of the swirl chamber until the velocity becamesubstantially zero at the discharge orifice. A zero velocity at thedischarge orifice requires that the axial acceleration of the swirlingair stream precisely at the discharge orifice must be extremely high inorder to transform the axial velocity at that pointfrom nearly zero tofull burner discharge velocity. Now, the only forcetending to axiallyaccelerate the swirling mixture of air and oil in a burner nozzlethrough the dischargeorifice is the pressure of the air charged to theswirl chamber, since this pressure isthe only external force applied tothe nozzle, theliquid oil being under'atmospheric pressure. At aconstant pressure of air charged to the nozzle, the axial force tendingto axially accelerate the swirlingmixture of air and oil in an axialdirection through the discharge orifice remains constant. According tothelaw: Force=Mass Accel eration, at a constant air pressure the productof mass moving axially through the nozzle-times the axial dischargeacceleration is also a constant. If theaxial velocity at thedischargeorifice is almost zero, as would occur with a hemisphericall yshaped swirl chamber, the axial acceleration to full burner axialdischarge velocity which occurs at the discharge orifice is necessarilylarge, and therefore the amount of mass that can be carried axiallythrough the discharge orifice is relatively small. Since most of themass in a swirling mixture of air and liquid oil is comprised of theheavier liquid oil, the relatively light air will move forwardly throughthe discharge orifice leaving the relatively heavy liquid oil within theswirl chamber.

The use of a conical or cylindrical swirl chamber, in contrast to aswirl chamber wall surface configuration which causes a reduction inaxial velocity of the swirling gas stream as it travels within the swirlchamber, such as a hemispherical swirl chamber, is critical when anozzle is utilized for purposes of aspiration; When the swirl chamberwall converges conically from a position to the rear of theaxialterminus of the tubular duct to the discharge orifice, which is thenarrrowest portion of the forward discharge passage, or has the contourof a uniform cylinder over the same region, theforward or axialcomponent of velocity of a swirling gas stream remains uniform fromtherear to the front of the swirl chamber, so that at the dischargeorifice the swirling stream does not have to accelerate in a forwarddirection from a substantially zero forward velocity to full axialdischarge velocity. With a conical or cylindrical swirl chamber, theforward velocity of the swirling stream is substantially the same at thefront and rear of the swirl chamber, but with a hemispherical swirlchamber there occurs a continual decrease of the axial velocity of aswirling gas stream until its forward velocity is nearly zero near thedischarge orifice.

Eventhough the swirl chamber wall surface of this invention converges asa substantially-uniform hollow cone or extends as a substantiallyuniformhollow cylinder from a position to the rear of the axial terminusof the tubular duct to the discharge orifice, it is also critical thatthis conical or cylindrical configuration extend all the way back to theswirling means and that no portion of the swirl chamber wall surfacediverge in front of the swirling means. A diverging swirl chamber wallsurface in front of the swirling means causes expansion of thepressurized swirling gas and thereby induces loss of swirling velocity.The only way to increase such lost swirling velocity is to increase thepressure of the aspirating gas. However, an increase in aspirating gaspressure tends to 1O flood the swirl chamber with pressurized air,thereby reducing aspiration therein.

The diameter of a cylindrical swirl chamber of this inventionispreferably about 1.5 to 3 times the internal diameter of its associatedaxial du-ct for optimum aspiration through the duct. The length of acylindrical swirl chamber is preferably no greater than'its diameter.However, these dimensions are merely preferable and a wide range ofdimensions can be utilized with good results. Whatever dimensions areoptimum for a particular nozzle it is highly important that acylindrical swirl chamber be uniformly cylindrical along its entire-length.- For example,

if a cylindrical swirl chamber tends to diverge conically along itslength, with the larger opening of the cone exposed to the atmosphere,the centrifugal'effect in the swirling gas stream will cause the streamto diverge in passing the axial duct opening thereby forming aprogressively growingcentra'l vortex. The diameter of the-vortex willbethelargest upon exposure to -the atmosphere; Such an arrangement wouldpermit easy access of the atmosphere to the vortex, thereby'sharplyreducing or destroyingits vacuum; It is seen that a diverging flow ofthe aspirating gas in passing the terminal opening of the axial tubeexposes a larger vortex diameter to the atmosphere than that exposed tothe axial inlet tube, thereby permittingtheatmosphere to destroythevacuum and preventing fluid aspiration through the tube. In such a case,the'problem becomes enhanced if the length of the swirl chamber isgreat, especially if the length of the swirl chamber is greater than thediameter of the swirl chamber.

The adverse effect of'a swirling gas stream progressively diverging inits passage by the axial duct opening during its transit to theatmosphere is avoided by employing a swirl chamber which is either auni-form cylinder or is a converging cone. With these swirl chamberconfigurations, the diameter of the discharge orifice is no larger thanthe diameter at any intermediate point inside the swirl chamber withwhich it is associated, and the vortex .of the swirling gas in theregion of exposure tothe atmosphere therefore cannot be larger than thevortex of the swirling gas in the'region to which the axial duct openingis exposed. With this construction the difliculty of the atmospheredestroying the vacuum at the swirling gas vortex is substantiallyavoided and aspiration of fluid through the axial duct is enhanced.

It was found that if the axial inlet port and the'tangential aspiratinggas openings are both flush with the base of an aspirating swirlchamber, the aspirating gas is unable to effect aspiration of the fluidin the axial port. In a test made with such an apparatus, aspirating airwas unable to aspirate suflicient fuel oil to discharge a combustiblemixturefrom the nozzle.

It was further found by tests that the exterior surface of the axialinlet duct must extend longitudinally parallel to the nozzle axis. Itwas found that if the exterior of the axial inlet du'ctconstituted acone with its broad base coincident-with the rear of the swirl chamberand its smaller base closest to the swirl chamber orifice, it'was notpossible to aspirate suflicient fuel to discharge a combustible mixturefrom the nozzle. It was also found that if the exterior of the axialinlet duct is hemispherical in shape with the base of the hemispherecoincident with the rear wall ofthe swirl chamber it was not possible toaspirate suificient fuel to discharge a combustible mixture from thenozzle. In contrast, when an axial duct whose exterior surface had acylindrical shape was employed highly satisfactory combustion wasachieved. The reason evidently is that a portion of the pressurizedaspirating air expands toward the center of the swirl chamber uponentering the swirl chamber and, when employing a conical orhemispherical axial duct, this air is caused to flow past the portopening in a direction at least partially transverseto the opening,thereby blocking the opening. On the other hand, with a cylindricalaxial duct the only axial component of movement of the expanding airtraveling in the immediate region of the duct opening is completelyparallel to the opening thereby preventing back pressure against theopening and thereby allowing aspiration to proceed.

There is a functional advantage inherent in the use of an axial ductwhich is cylindrical over substantially its entire length whichadvantage occurs over and above avoidance of transverse air flow infront of the terminal duct opening. This advantage lies in the fact thatwhen the entire length of the axial duct is cylindrical the air adjacentto the duct flows in a direction which is parallel to the axis of theduct and thereby exerts a positive aspirational effect at the ductopening in its own right, aside from avoidance of the negative effect oftransverse obstruction of the duct opening. Therefore, when parallelflow past the duct opening occurs two benefits are obtained: first,obstruction of the duct opening is avoided and, secondly, an additionalaspirational effect is exerted at the duct opening.

The axial du-ct through which a fluid is being aspirated should notterminate at the beginning of the discharge orifice of a conical swirlchamber. The reason is that air traveling along the wall of a conicalswirl chamber will be directed transversely across the opening of theaxial duct at that position and thereby inhibit or prevent aspirationthrough the duct.

In order to insure that the fluids being aspirated enter the nozzlesolely through the effect of aspiration it is advantageous that no levelof these fluids exist above the nozzle and that these fluids be drawnfrom supply reservoirs which are exposed to the atmosphere and locatedbelow the nozzle. In this manner, when the aspirating gas supply to thenozzle is interrupted and the suction effect disappears no dripping offluids such as oil from the nozzle occurs as often does occur in asystem 'wherein the oil is supplied to the nozzle under pressure ratherthan by aspiration.

In order to prevent interference with the aspirating gas, the nozzle ofthis invention is free of means tending to impart swirling to the liquidflowing within and emerging from the axial duct in the first swirlchamber. Thereby, the liquid emerging from the first swirl chamber axialduct enters the first swirl chamber in a purely axial direction and doesnot interfere with the motion of the swirling gas within the swirlchamber. In contrast, if the liquid were to exit from axial duct with aswirling motion, upon entering the swirl chamber it would tend to beflung radially under centrifugal force, thereby directly intruding uponthe swirling gas stream and tending to interfere with the motion of theswirling gas stream within the swirl chamber. Since it is the swirlingmotion of the gas stream which provides the means for aspiration, anyinterference with this stream is an interference with the heart ofnozzle operation.

In the nozzle of this invention, it is important that the diameter ofthe discharge orifice is larger than the internal diameter of the axialtubular duct. The reason is that the discharge orifice must besufficiently large to discharge the liquid being aspirated through thetubular duct plus a relatively large volume of aspirating gas. If thediameter of the discharge orifice is the same size as the internaldiameter of the tubular duct it will only be large enough to freelydischarge the aspirated liquid. Unless the diameter of the dischargeorifice is larger than the internal diameter of the tubular duct, itwill not be sufliciently large to freely discharge both the aspiratedliquid and the relatively large volume of swirling gas, and willtherefore obstruct discharge from the nozzle and thereby preventaspiration.

The swirl chamber of the nozzle of this invention is provided with rearenclosure means extending from the exterior of the axial tubular duct sothat the swirl chamber is substantially completely enclose-d at the rearthereof and the openings of the swirling means extend through not morethan a minor proportion of the surface of the rear wall of the swirlchamber. The openings of the swirling means are thereby restricted bythe swirl chamber wall rear enclosure. These openings are directed intothe swirl chamber in not only a tangential direction but also in aforwardly direction with respect to the conical or cylindrical swirlchamber wall surface which surrounds the open terminus of the axialtubular duct. This structure is extremely critical to the function of anaspirating nozzle, especially if the aspirating nozzle is utilized as anoil burner. A swirling air aspirating nozzle performs its aspiratingfunction by establishing a highly evacuated central vortex at the centerof a swirling gas stream which induces aspiration of liquid oil. Toestablish a highly evacuated central vortex, it is necessary that only alimited quantity of pressurized swirling air be charged to the swirlchamber and that this air be discharged from the swirl chamber asrapidly as possible because if an excessive quantity of air is chargedto the swirl chamber or is permitted to accumulate within the swirlchamber it will fill the entire chamber, thereby flooding the chamberand filling the axial region thereof with air, preventing the formationof an evacuated axial vortex. Excessive inflow of pressurized air isprevented by utilizing rear enclosure means in the swirl chambersurrounding the exterior of the tubular duct so that the majorproportion of the rear wall surface of the swirl chamber is enclosed,with the swirling opening means extending through not more than a minorproportion of the rear wall of the swirl chamber. In the absence of arear enclosure means, air could swirl within the swirl chamber but theamount of air admitted would be so excessive that the chamber wouldbecome flooded with pressurized air and an evacuated vortex adequate toaccomplish aspiration could not possibly form. Also, excessiveaccumulation of pressurized air within the swirl chamber is prevented bydirecting the aspirating air into the swirl chamber in a forward as wellas a tangential direction so that the swirling air rapidly travels tothe discharge orifice of the swirl chamber. Tangential but non-forwardadmission of pressurized air would tend to cause the air to swirl insitu at the rear of the swirl chamber, and thereby accumulate within theswirl chamber, flooding the swirl chamber with air.

Not only is the rear of the swirl chamber enclosed but also the swirlingmeans opens into the swirl chamber only at the converging conical'swirlchamber wall surface or the cylindrical swirl chamber wall surfaceextending past the terminus of the tubular duct. It is critical that theswirling means open into the swirl chamber only at a position laterallyremote from the tubular duct in order to supply a jet of pressurized airdirectly at the curved swirl chamber wall surface entirely remote fromthe tubular duct. In this manner, the air swirls as a thin film in closeproximity to the swirl chamber wall surface permitting the axial portionof the swirl chamber to remain relatively free of pressurized gas.

If a nozzle does not possess enclosure means at the rear of the swirlchamber to restrict the volume of pressurized air flow, even if itsucceeds in aspirating a small quantity of fuel it could not function asa burner nozzle. The reason is that if too much pressurized air isadmitted to a burner nozzle swirl chamber, the air exit velocity at thenozzle discharge orifice will become greater than the velocity of flamepropagation, and the nozzle will not be able to maintain a flame. Thisis a common phenomenon and is often observed in a blow torch. As thevelocity of the combustion mixture being discharged from a blow torchincreases the flame can be observed to move progressively further awayfrom the torch until it finally disappears. The flame disappearscompletely when the exit velocity of the combustion gas mixture becomesappreciably greater than the velocity of flame propagation. Thisphenomenon is commonly observed in aspirating burner nozzles wherein astream of swirling air aspirates fuel oil. When an aspirating nozzle is13 employed as an oil burner, provision of enclosure means at the rearof the swirl chamber to restrict the volume of pressurized air flow istherefore highly critical in order to prevent the aspirating airdischarge velocity from becoming greater than the velocity of flamepropagation.

It is seen that there is a critical upper limit for the dischargevelocity from a burner nozzle. Therefore, there is a critical upperlimit to air flow rate through an aspirating nozzle swirl chamberbecause at any given air flow rate, nozzle discharge velocity cannot bediminished by arbitrarily increasing the size of the discharge orificesince an increase in discharge orifice size tends to destroy the vacuumwithin the nozzle by permitting access of the atmosphere thereto.However, it has been found to be highly advantageous in a burner nozzleto admix with the aspirated oil an amount of pressurized air in excessof the critical upper limit thatcan be passed through an aspiratingnozzle swirl chamber. In accordance with the present invention, theadditional pressurized airis advantageously supplied by employing asecond swirl chamber in the nozzle in. series with the aspirating swirlchamber with the second swirl chamber having a discharge orifice largerthan that of the aspirating chamber. Secondary pressurized air isadmitted to the second swirl chamber in a forward and tangentialdirection with respect to the second swirl chamber wall surface and thesecond swirl chamber is otherwise constructed in the manner ofan'aspirating swirl chamber of the present invention so that the mixtureof swirling air and oil from the aspirating swirl chamber is admitted tothe second swirl chamber through a cylindrical axial duct extending fromthe aspirating swirl chamber discharge orifice to an intermediate axialposition in the second swirl chamber. This discharge orifice of thesecond swirl chamber is larger than the discharge orifice of the firstchamber by an amount adequate to accommodate the discharge of the.secondary air in addition to the air-oil mixture from the aspiratingswirl chamber. in this manner, the secondary air does not inhibitaspiration by flooding, the aspirating chamber, because it is notadmitted to the aspirating chamber, nor does it increase the nozzledischarge velocity beyond'its critical upper limit, becauseof the use ofthe larger discharge orifice. If desired, more than one additional swirlchamber can be provided in series with an aspirating swirl chamber, withswirling pressurized air admitted to each additional swirl chamber'andwith each succeeding discharge orifice being larger insize than itspredecessor discharge orifice.

In all aspirating nozzles of this invention, it has been foundadvantageous to employ a forward chamber which does not have aspirationas its primaryfunction but which functions to enrich the mixture fromthe aspirating swirl chamber with a swirling stream of secondary air.The employment of a forward pressurized air swirl chamber inanaspirating burner nozzle of this invention was found 'togreatly improvethe flame produced upon combustion of an air-oil spray therefrom, ascompared to the flame produced in its absence, in respect to both flamecompactness and smoke reduction.

In a multiple swirl chamber nozzle of this invention, his critical thateach swirl chamber to which a pressurized fluid is charged possess allthe essential structure of a single swirl chamber nozzle, except thateach swirl chamber which is forward with respect to the first swirlc'h'amberwill receive a swirling mixture through the axial ductextending thereinto. The wall surface of the first and forward swirlchambers in a multiple swirl chamber nozzle can both have a conicalconfiguration or they both can have a cylindrical configuration. Ifdesired, the first swirl chamber can have a conical wall surface withthe forward swirl chamber having a cylindrical wall surface, or viceversa. In a series of swirl chambers in a single nozzle, conical orcylindrical wall surface configuration can be utilized in anycombination as long as each swirl chamber to which a pressurized fluidis charged 14 possesses all the essential structure of a single swirlchamber nozzle.

In accordance with this invention, a spray comprising a mixture ofpressurized air and aspirated oil suitable for combustion is prepared bycharging a stream or jet of pressurized air in a forward andsubstantially. tangential direction along a swirl chamber surface at therear thereof. The jet impinges upon the swirl chamber surface along onlya minor proportion of the circumference thereof and spreads sidewaysalong said surface so that the major proportion of the pressurized airswirls along the swirl chamber surface as a film which is thin relativeto the swirl chamber cross section allowing an axial evacuated vortex toform within said swirl chamber. The open end of a duct containing fueloil under a pressure lower than that of the pressurized air andpreferably under substantially atmospheric pressure is axially exposedto the vortex. The only axial component of movement of the pressurizedair which expands into the region surrounding said fuel oil duct openingis parallel to the axis ofthe swirl'chamber. The swirling air streamtravels the length of said swirl chamber at a substantiallyuniform'axial velocity. The fuel oil is aspirated into the vortex of theswirling gas stream. The amount or pressure of the air admitted to theswirl chamber is adjusted so as to be sutfi-ciently high to produce acombustible spray mixture but sufficiently smallso that the spraymixture of'swirling air and aspirated oil is discharged from the nozzleat a velocity which is not appreciably greater than-the velocity offlame propagation.

In nozzles wherein more than one fluid is aspirated inwardly by means ofthesuction exerted at the vortex of aswirling gas stream, a variety ofstructures can be employed. In one embodiment, a plurality of coaxial,concentric cylindrical ducts extend into the rear of a swirl chamber tovarious intermediate points along the axis thereof, the innermostconcentric duct extending farthest into the swirl chamber, the duct nextsurrounding the innermost duct extending a smaller distance into theswirl chamber, etc. The outermost duct extends the smallest distanceinto the swirl chamber but even this outermost duct extends a greaterdistance from the'rear of the swirl chamber than does the tangentialopeningfor the admittance of aspirating gas. In this arrangement ofcoaxial, concentric cylindrical duets, with each inner concentric ductextending a greater axial distance into the swirl chamber than its nextadjacent outer duct and with even the outermost concentric ductextending a greater distance from the rear of the swirl chamber than thedistance of the aspirating gas inlet port from the rear of the swirlchamber, each concentric duct connects the swirl chamber and itsrespective reservoir of fluid, which reservoir is disposed below thenozzle, and each duct preferably extends into its respective reservoirdownwardly through the level of fluid contained therein.

In nozzles'wherein more than one fluid is aspirated inwardly by means ofthe suction exerted at the vortex of a swirling gas, concentricarrangement of the axial ducts permits maximum proximity of the fluidsunder aspiration to the axis of the swirl chamber, which is the zone ofgreatest vacuum. In this arrangement, the staggetting of duct lengths,as described, permits a high degree of uniformity of exposure of theplurality of fluids under aspiration to thevortex of surroundingswirling fiuid. In operation, the vortex of the aspirating gas drawsinto the swirling stream of aspirating gas a first fluid enteringthrough the outermost annular space formed by the concentric ducts toproduce a first mixture comprising aspirating gas and said first fluid.The greater length of the next adjacent annular space allows this firstmixture to form an adequate swirl pattern and vortex prior to drawinginto itself a second fluid through the next adjacent annular space toform a second mixture comprising aspirating gas, first fluid and secondfluid. Again, the increasing length of each adjacent annular spaceallows this second mixture to form anadequate swirl pattern and vortexprior to aspirating a third fluid to form a third mixture comprisingaspirating gas and said first, second and third fluids. In a likemanner, the fluid in each subsequent duct is aspirated into the nozzle.The preferred number of concentric tubes is two: a first fluid in theinner tube being exposed to the axis of the swirl chamber, which is thezone of greatest vacuum, and the inner tube extending a greater distanceinto the swirl chamber than the outer tube. In this arrangement, asecond fluid enters the swirl chamber through the annular space betweenthe two tubes.

Because of size limitation in burner nozzles it is often essential thatmultiple fluid aspirating nozzles which are to be employed as burnershave multiple, coaxial chambers. When employing a nozzle having only onechamber it is necessary to aspirate all the fluids into a single chamberwhich necessitates severe restriction of duct passages. As alreadynoted, when fuel oil is the fluid being passed through a nozzle,restriction of duct passages is conducive to plugging. However, with amultiplicity of chambers an apportioning of the fluids under aspirationbetween the available chambers is possible, thereby avoiding restrictionof duct passages in any single chamber. In a multiple chamber nozzle itis preferable to aspirate only a single fluid into the first chamberthrough a cylindrical axial duct extending to an intermediate pointalong the length of said chamber. The mixture emitted from this firstchamber is then discharged through an axial orifice at the forward endof the first chamber which leads to a second chamber coaxial with thefirst, also having an axial orifice at its forward end and having atleast one side port, preferably tangential, for the admission of asecond fluid by means of aspiration. Subsequent chambers substantiallysimilar to the second chamber can be employed.

The mixture emitted from the first chamber can enter the second chamberat an intermediate position along the length of the second chamber bymeans of a duct extending thereto from the first orifice. Such a duct ispreferably generally cylindrical and has approximately the diameter ofthe orifice from which it protrudes. The diameter of the second chamberis larger than the diameter of this duct thus providing an annulusthrough which the first mixture exerts an aspirational effect. Theaspirational effect draws the second fluid through the annulus into thefirst mixture. The quantity of second fluid aspirated is dependent uponthe diameter differential between the second chamber and the duct. Ofcourse, at a zero diameter differential no opening exists and thereforeno aspirational flow occurs. ential increases the rate of fluidaspiration correspondingly increases until a maximum rate occursfollowing which a further slight diameter differential increase causes asharp reduction in the rate of aspiration of the second fluid.

The use of a duct extending from the first orifice to an intermediateaxial position along the length of the second chamber provides theadvantage of accurate delineation of the smaller diameter of the optimumdiameter differential. However, we have found that it is possible toaspirate the second fluid at a greater rate in the absence of such aduct. In the absence of the duct, the mixture is projected forwardly andradially from the first orifice as a conical spray. The divergence ofthe spray requires the diameter of the second chamber to be somewhatlarger, for maximum aspirational rates, than the diameter required whenthe aforementioned duct is utilized. In the absence of a duct, as is thecase when a duct is employed, increasing the diameter of the secondchamber from the size corresponding to a minimum aspirational rateinduces a corresponding increase in rate of aspiration of the secondfluid. This increase continues until a maximum aspiration rate occurswhereupon a further slight increase in the diameter of the secondchamber results in a sharp reduction of rate of aspiration of the secondfluid.

As the diameter differ- We claim:

ll. An aspirating nozzle comprising in series coaxial first swirlchamber means and forward swirl chamber means, each of said swirlchamber means being enclosed and having a curved wall to provide asubstantially circular cross section, axial discharge opening means atthe forward end of each of said swirl chamber means the narrowestportion of which constitutes discharge orifice means, opening means forswirling at the rear of each swirl chamber means adapted for admissionof swirling pressurized gas to each swirl chamber means, each openingmeans for swirling in said nozzle associated with tubular duct meansextending axially from the rear of the swirl chamber means andterminating with tubular duct axial opening means at an intermediateaxial position in the swirl chamber means between theopening means forswirling and said discharge orifice means, the tubular duct terminatingin each forward swirl chamber means originating at the discharge orificeof the swirl chamber to its rear, the diameter of the discharge orificemeans in a swirl chamber being larger than the internal diameter of thetubular duct means terminating in that swirl chamber, the wall surfaceof the first swirl chamber means extending as a substantially uniformcylinder from said opening means for swirling disposed to the rear ofthe axial terminus of the tubular duct means therein to its dischargeorifice means, the wall surface of the forward swirl chamber meansconverging substantially conically from a position to the rear of theaxial terminus of the tubular duct means therein to its dischargeorifice means, the outer surface of each tubular duct means having theconfiguration of a cylinder over substantially its entire length, saidfirst swirl chamber being free of means for imparting swirling to afluid flowing from the tubular duct means terminating therein, eachswirl chamiber means having rear enclosure means extending between theexterior of the tubular duct means terminating therein and its curvedswirl chamber wall surface so that each swirl chamber means issubstantially completely enclosed at the rear thereof, each openingmeans for swirling extending through not more than a minor proportion ofthe surface of the rear wall of its swirl chamber means, each openingmeans for swirling disposed only at the converging conical orcylindrical wall surface of its swirl chamber laterally remote from itsassociated tubular duct means and rearwardly with respect to the axialterminus of its associated tubular duct means, each opening means forswirling directed into its swirl chamber means in both a forwardly andsubstantially tangential direction with respect to its curved swirlchamber wall surface adapted for the admission to each swirl chambermeans of a swirling pressurized gas'in both a forwardly andsubstantially tangential direction with respect to the curved swirlchamber wall surface thereof.

2. An aspirating nozzle comprising in series coaxial first swirl chambermeans and forward swirl chamber means, each of said swirl chamber meansbeing enclosed and having a curved wall to provide a substantiallycircular cross section, axial discharge opening means at the forward endof each of said swirl chamber means the narrowest portion of whichconstitutes discharge orifice means, opening means for swirling at therear of each swirl chamber means adapted for admission of swirlingpressurized gas to each swirl chamber means, each opening means forswirling in said nozzle associated with tubular duct means extendingaxially from the rear of the swirl chamber means and terminating withtubular duct axial opening means at an intermediate axial position inthe swirl chamber means between the opening means for swirling and saiddischarge orifice means, the tubular duct terminating in each forwardswirl chamber means originating at the discharge orifice of the swirlchamber to its rear, the diameter of the discharge orifice means in aswirl chamber being larger than the internal diameter of the tubularduct means terminating in that :17 swirl chamber, the wall surface ofthe first swirl chamber means extending as a substantially uniformcylinder from said opening means for swirling disposed to the rear ofthe axial terminus of the tubular duct means therein to [its dischargeorifice means, the wall surface of the forward swirl chamber meansconverging substantially conically from a position to the rear of theaxial terminus of the tubular duct means therein to its dis-chargeorifice means, the outer surface of each tubular duct means having theconfiguration of a cylinder over substantially its entire length, eachswirl chamber means having rear enclosure means extending between theexterior of the tubular duct means terminating therein and its curveswirl chamber wall surface so that each swirl chamber means issubstantially completely enclosed at the rear thereof, each opening 15means for swirling extending through not more than a minor proportion ofthe surface of the rear wall of its swirl chamber means, each openingmeans for swirling disposed only at the converging conical orcylindrical wall surface of its swirl chamber laterally remote from itsassociated tubular duct means and rearwardly with respect to the axialterminus of its associated tubular duct means, each opening means forswirling directed into its swirl chamber means in both a forwardly andsubstantially tangential direction with respect to its curved swirlchamber Wall surface adapted for the admission to each swirl chambermeans of a swirling pressurized gas in both a forwardly andsubstantially tangential direction with respect to the curved swirlchamber wall surface thereof.

No references cited.

EVERETT W. KIRBY, Primary Examiner.

1. AN ASPIRATING NOZZLE COMPRISING IN SERIES COAXIAL FIRST SWIRL CHAMBERMEANS AND FORWARD SWIRL CHAMBER MEANS, EACH OF SAID SWIRL CHAMBER MEANSBEING ENCLOSED AND HAVING A CURVED WALL TO PROVIDE A SUBSTANTIALLYCIRCULAR CROSS SECTION, AXIAL DISCHARGE OPENING MEANS AT THE FORWARD ENDOF EACH OF SAID SWIRL CHAMBER MEANS THE NARROWEST PORTION OF WHICHCONSTITUTES DISCHARGE ORIFICE MEANS, OPENING MEANS FOR SWIRLING AT THEREAR OF EACH SWIRL CHAMBER MEANS ADAPTED FOR ADMISSION OF SWIRLINGPRESSURIZED GAS TO EACH SWIRL CHAMBER MEANS, EACH OPENING MEANS FORSWIRLING IN SAID NOZZLE ASSOCIATED WITH TUBULAR DUCT MEANS EXTENDINGAXIALLY FROM THE REAR OF THE SWIRL CHAMBER MEANS AND TERMINATING WITHTUBULAR DUCT AXIAL OPENING MEANS AT AN INTERMEDIATE AXIAL POSITION INTHE SWIRL CHAMBER MEANS BETWEEN THE OPENING MEANS FOR SWIRLING SAID SAIDDISCHARGE ORIFICE MEANS, THE TUBULAR DUCT TERMINATING IN EACH FORWARDSWIRL CHAMBER MEANS ORIGINATING AT THE DISCHARGE ORIFICE OF THE SWIRLCHAMBER TO ITS REAR, THE DIAMETER OF THE DISCHARGE ORIFICE MEANS IN ASWIRL CHAMBER BEING LARGER THAN THE INTERNAL DIAMETER OF THE TUBULARDUCT MEANS TERMINATING IN THAT SWIRL CHAMBER, THE WALL SURFACE OF THEFIRST SWIRL CHAMBER MEANS EXTENDING AS A SUBSTANTIALLY UNIFORM CYLINDERFROM SAID OPENING MEANS FOR SWIRLING DISPOSED TO THE REAR OF THE AXIALTERMINUS OF THE TUBULAR DUCT MEANS THEREIN TO ITS DISCHARGE ORIFICEMEANS, THE WALL SURFACE OF THE FORWARD SWIRL CHAMBER MEANS CONVERGINGSUBSTANTIALLY CONICALLY FROM A POSITION TO THE REAR OF THE AXIALTERMINUS OF THE TUBULAR DUCT MEANS THEREIN TO ITS DISCHARGE ORIFICEMEANS, THE OUTER SURFACE OF EACH TUBULAR DUCT MEANS HAVING THECONFIGURATION OF A CYLINDER OVER SUBSTANTIALLY ITS ENTIRE LENGTH, SAIDFIRST SWIRL CHAMBER BEING FREE OF MEANS FOR IMPARTING SWIRLING TO AFLUID FLOWING FROM THE TUBULAR DUCT MEANS TERMINATING THEREIN, EACHSWIRL CHAMBER MEANS HAVING REAR ENCLOSURE MEANS EXTENDING BETWEEN THEEXTERIOR OF THE TUBULAR DUCT MEANS TERMINATING THEREIN AND ITS CURVEDSWIRL CHAMBER WALL SURFACE SO THAT EACH SWIRL CHAMBER MEANS ISSUBSTANTIALLY COMPLETELY ENCLOSED AT THE REAR THEREOF, EACH OPENINGMEANS FOR SWIRLING EXTENDING THROUGH NOT MORE THAN A MINOR PROPORTION OFTHE SURFACE OF THE REAR WALL OF ITS SWIRL CHAMBER MEANS, EACH OPENINGMEANS FOR SWIRLING DISPOSED ONLY AT THE CONVERGING CONICAL ORCYLINDRICAL WALL SURFACE OF ITS SWIRL CHAMBER LATERALLY REMOTE FROM ITSASSOCIATED TUBULAR DUCT MEANS AND REARWARDLY WITH RESPECT TO THE AXIALTERMINUS OF ITS ASSOCIATED TUBULAR DUCT MEANS, EACH OPENING MEANS FORSWIRLING DIRECTED INTO ITS SWIRL CHAMBER MEANS IN BOTH A FORWARDLY ANDSUBSTANTIALLY TANGENTIAL DIRECTION WITH RESPECT TO ITS CURVED SWIRLCHAMBER WALL SURFACE ADAPTED FOR THE ADMISSION TO EACH SWIRL CHAMBERMEANS OF A SWIRLING PRESSURIZED GAS IN BOTH A FORWARDLY ANDSUBSTANTIALLY TANGENTIAL DIRECTION WITH RESPECT TO THE CURVED SWIRLCHAMBER WALL SURFACE THEREOF.